The present invention relates to an image reading device, and more particularly to an image reading device including an illuminating means for illuminating a subject or an original bearing image information with light applied in a predetermined direction and an image reading means for reading in a predetermined direction light reflected by the original. so that extraneous reflections from the surface of the original and an image of edges of the original which is attached to a mount can be removed.
In printing and platemaking industries, image scanning reading/reproducing systems are widely used for electrically processing image information on subjects or originals to produce film original plates with a view to simplifying the printing or platemaking process and improving the quality of images which are read or reproduced.
Such an image scanning reading/reproducing system is basically constructed of an image reading device and an image reproducing device. In the image reading device, image information on a subject or an original which is fed in a sub-scanning direction is illuminated or irradiated in a main scanning direction by an illuminating means. Light reflected by the original is read by an image reading means and converted thereby to an electric signal representing image information. Then, the image information which has been photoelectrically converted by the image reading device undergoes various processes such as for gradation conversion, profile emphasis, and the like depending on platemaking conditions. Thereafter, the image information thus processed is employed to reproduce an image on an image recording medium made of a photographic film or the like. The image recorded on the image recording medium is then developed by an image developing device, and the developed image recording medium is used as a film plate for printing operation or the like.
Originals or subjects which carry image information to be read by the image reading device are often in the form of photographs or the like which are attached to mounts. Since such an original has a certain thickness. a shade is produced by its peripheral edges when it is illuminated by light and a read image of the original contains a mark or trace of the peripheral edges of the original.
The above problem will be described in greater detail with reference to FIG. 9 of the accompanying drawings which shows an image reading device. In the image reading device, a mount 4 to which an original 2 is attached is fed in the direction indicated by the arrow X, while at the same time the surfaces of the original 2 and mount 4 are illuminated obliquely by illuminating light L. emitted from a light source 6. Light R reflected by the illuminated surfaces is detected by a CCD (charge-coupled device) camera 8 and converted to an electric signal. The attached original 2 has a certain thickness, it produces a shade 10 around the peripheral edges thereof where no illuminating light is applied. The CCD camera 8 therefore reads the image information of the attached original 2 as well as the image information of the shade 10. As a result. the reproduced image contains a mark or trace of the shade 10 around the original 2.
One solution is to position another light source 12 in substantially symmetric relation to the light source 6 with respect to the reflected light R. The shade 10 can be removed by applying illuminating light L.sub.1 from the light source 6 and illuminating light L.sub.2 from the light source 12 to the original 2 and the mount 4.
However, the entire arrangement shown in FIG. 9 is large, complex, and expensive because of the two light sources 6, 12 required. If the subject or original 3 and the mount 4 are positionally displaced, then the positions where they are illuminated by the illuminating light L.sub.1, L.sub.2 are separated from each other or brought out of alignment, resulting in an irregularity in the image read by the CCD camera 8.
In cases where the original 2 which carries image information is in the form of photographic paper that produces surface reflections, the reproduced image becomes poor in quality when such surface reflections are detected by the CCD camera 8. Specifically, if the original 2 is in the form of a matte surface photographic paper, it is known that surface reflections are present within a range of about .+-. 45.degree. from the specular or regular reflection of the incident illuminating light L.sub.1. In order to prevent the surface reflections from reaching the CCD camera 8, the light source 6 must be positioned such that the angle .theta. formed between the illuminating light L.sub.1 and the reflected light R is about .+-. 45.degree. or greater. Therefore. the position of the light source 6 is largely limited, and the intensity of the reflected light R which reaches the CCD camera 8 is reduced since the angle .theta. is large. With the two light sources 6, 12 used, inasmuch as the angle .theta. is large, the positions a illuminated by the illuminating light L.sub.1, L.sub.2 are displaced to a larger extent when the attached original 2 and the mount 4 are positionally varied. Should this happen, the image read by the CCD camera 8 suffers greater irregularities, and hence no accurate image can be obtained.